Forget shuffleboard and croquet. With Americans living longer, a growing number of people are embarking on entrepreneurial second careers -- well into their 80s. Indeed, for many, running a company has become the new retirement. So what are the real secrets to longevity, in business and in life?

When he's not jetting off to Africa, to oversee an American-style hospital his architecture firm is designing, 81-year-old Bernard Rothzeid is back in New York, sketching, brokering new deals, and breaking bread with clients.

Iris Rubinfield helped her husband build a successful manufacturing company. When he passed away, she suddenly found herself at the helm. Nearly three decades later, she's transformed it into one of America's fastest-growing private companies.

Jack Weil's clothing company, Rockmount Ranch Wear, was made popular by the likes of Clark Gable, Elvis, and other celebrities. Today, Weil still keeps the customers coming in droves. Oh, did we mention he's 106? Meet the oldest entrepreneur in America.

Like millions of women, Lisa Gable was often frustrated by falling bra straps. So, at age 70, she designed a solution and launched an intimate apparel company. Fourteen years later, she's still at the helm -- and her Strap-Mate can be found at Nordstrom and other major retailers.